Add usage/benchmark info to README

README.md

 # cidranger
-IP to belonging CIDR block(s) lookup
+Fast IP to belonging CIDR block(s) lookup using trie implementation, e.g. 192.168.0.1 is contained in 192.168.0.0/24
 
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+### Usage
+Configure imports.
+```
+import (
+  "net",
+  
+  "github.com/yl2chen/cidranger"
+)
+```
+Creates a new ranger inmplemented using Level-Path-Compressed (path compressed capability coming soon) trie.
+```
+ranger := NewLPCTrieRanger()
+```
+Inserts CIDR blocks.
+```
+_, network1, _ := net.ParseCIDR("192.168.1.0/24")
+_, network2, _ := net.ParseCIDR("128.168.1.0/24")
+ranger.Insert(*network1)
+ranger.Insert(*network2)
+```
+The prefix trie can be visualized as:
+```
+0.0.0.0/0 (target_pos:31:has_entry:false)
+| 1--> 128.0.0.0/1 (target_pos:30:has_entry:false)
+| | 0--> 128.168.1.0/24 (target_pos:7:has_entry:true)
+| | 1--> 192.168.1.0/24 (target_pos:7:has_entry:true)
+```
+To test if given IP is contained in constructed ranger, IPv6 is not currently supported, an error will be returend if called with an IPv6 ip.
+```
+contains, err = ranger.Contains(net.ParseIP("128.168.1.0")) // returns true, nil
+contains, err = ranger.Contains(net.ParseIP("192.168.2.0")) // returns false, nil
+```
+To get all the networks given is contained in,
+```
+containingNetworks, err = ranger.ContainingNetworks(net.ParseIP("128.168.1.0"))
+```
+
+### Benchmark results comparing hit/miss for LPC trie vs brute force implementation, using AWS published ip ranges.
+```
+BenchmarkLPCTrieHitUsingAWSRanges-4        	   5000000	      256.00 ns/op
+BenchmarkBruteRangerHitUsingAWSRanges-4    	    100000	    14739.00 ns/op
+BenchmarkLPCTrieMissUsingAWSRanges-4       	  20000000	       57.50 ns/op
+BenchmarkBruteRangerMissUsingAWSRanges-4   	     50000	    25038.00 ns/op
+```
+
+### TODO
+* Implement level-compressed component of LPC trie ranger.
+* Add support for IPv6